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Confluence of factors caused salmon collapse, report says

Posted by: Maven on March 19, 2009 at 8:08 am

From Mike Taugher at the Contra Costa Times:

The roots of last year’s unprecedented decision to close the California coast to salmon fishing took hold three years earlier, in the spring of 2005 when juvenile fish swam through the Golden Gate to an ocean lacking ample food for them, a new report says.

On the Farallon Islands bird sanctuary, nearly all the Cassin’s auklets, which eat the same kind of food as juvenile salmon, abandoned their nests that year. Gray whales that migrate along the coast were reported emaciated and sea lions were found searching for food far from shore. The salmon that would have returned to spawn in 2007 starved, or were weakened and eaten by other fish or birds. The same thing happened in 2006, causing low numbers to return again last year.

Naturally varying ocean conditions were the immediate cause of a fishing season closure for which $170 million in federal disaster funds were made available last year, according to a report released Wednesday by a team of scientists assigned last year to investigate the collapse.

From the San Francisco Chronicle:

“Poor ocean conditions triggered the collapse. But what primed it is the degradation of the estuary and river habitats and the heavy reliance on hatcheries over the years,” said Steve Lindley, lead author and a research ecologist at National Oceanic and Atmospheric Administration.

Over decades, construction of dams and other barriers, reliance on hatcheries and diversion of water from the Sacramento-San Joaquin River Delta have changed California’s chinook salmon from genetically diverse, naturally spawning wild populations to one dominated by fall chinook salmon from four large hatcheries, the study said.

When the Central Valley had many salmon runs, the fish would migrate to the ocean at different times, increasing their odds of surviving unpredictable conditions. But the biggest remaining run, the fall run, is heavy on hatchery fish that all migrate at once and can be wiped out by poor climate and sparse food.

Last year, for the first time in California history, commercial and sport fishing was banned. Two consecutive years of low returning spawners – 87,881 in 2007 and 66,286 in 2008 – indicate that the federal regulatory body, the Pacific Fishery Management Council, will set similar curbs for this year’s fishing season, which begins in May.

From the Eureka Times-Standard:

Management of the fishery also came under scrutiny. While a 2007 fishery council prediction anticipated that 265,000 salmon would return to the river — based on the 2-year-old fish that showed up the year before — only 88,000 adult salmon actually made it into the Sacramento. A bias in a forecast model was blamed for the discrepancy, the report reads, and contributed to the failure of the run to meet conservation goals.

The report suggested that simply increasing production from the Sacramento’s four main hatcheries, which produce mostly fall-run chinook salmon, might concentrate fish in time and space and make the system more vulnerable to boom-and-bust cycles. Naturally spawning fall salmon in the river are now genetically homogenous, the report reads, making them vulnerable.

National Marine Fisheries Service Supervisory Research Ecologist Steve Lindley said that hatcheries could be operated to release fewer fish at any one time, and release them at differing times, to create more variability that would help them ride out poor conditions in the ocean.

”In the longer term, the real key is improving naturally spawning fish,” Lindley said.

According to the Santa Rosa Press Democrat, water diversions are not necessarily to blame:

The study noted that delta water exports were at near-record levels during 2005 and 2006, the years when those fish were released from hatcheries into the river. But the diversions weren’t unusual in the months when the fish actually were in the river or San Francisco Bay en route to the ocean, said Churchill Grimes, director of NOAA’s National Marine Fisheries Service at the agency’s Santa Cruz Marine Laboratory.

“We’re not trying to be apologists for the water pumpers,” Grimes said. “That’s just what the numbers are.”

Fishermen said the report failed to account for why this year’s adult salmon are still in such low numbers when ocean conditions appear to have improved.

“We’re sorely disappointed that they failed to look at or fully understand delta flows for Sacramento River (salmon) survival, said Zeke Grader, executive director of the Pacific Coast Federation of Fishermen’s Associations.

March 19, 2009 · Filed Under Wildlife & Endangered Species

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